Response of an anaerobic fluidized bed reactor treating ice-cream wastewater to organic, hydraulic, temperature and pH shocks

Abstract

An anaerobic fluidized bed reactor, operating at 35° C, was used to treat ice-cream wastewater with an influent chemical oxygen demand (COD) of 5.2 g l −1. Start-up of the reactor was achieved within 30 days by use of a regime that included stepped increases in influent COD and methanol substitution of the substrate. A steady state was achieved with 94.4% COD reduction at an organic COD loading rate of 15.6 g l −1 d −1 (HRT 8 h). This rate is somewhat faster than those achieved in previously reported studies. The reactor was subjected to transient changes in temperature, pH, influent flow-rate and COD for 6 and 12 h periods. The quality of the effluent deteriorated under these shock load conditions but returned to steady-state values within 6–16 h upon restoring normal conditions. The stability of the reactor under unfavourable process conditions is discussed.